This type of electrode is called a liquid junction electrode. It means there is a fluid interface inside the frit between electrolyte from the RE and electrolyte from the cell. Therefore, the RE should slowly but constantly leak. You can observe that by touching the RE tip to the paper towel. You may not see that effect so imminent when using Vycor glass frit (some of the other RE suppliers), but that also means that the impedance of our RE is lower.